1998 YZ WR400F Getting no compression

chevymcdude1976

I recently was blessed with a 98' YZ WR400F and have been sinking money in it since I have got this bike. I bought a new timing chain/guides, new spark plug, hot start, shifter lever and, some other parts.However I have all the new parts in the bike and it is in the correct time, but did not put the hot start on yet. My problem is,there is no compression, the pedal goes clear to the floor, can be pushed with your hand. I have been told by several people and different shops, numerous things it could be. I just now bought a new jug ( cylinder) and it comes with a piston. I need to know why and what would make my bike not get any compression. If someone can help, your input is much needed.